An extensible flexible hose, in particular but not exclusively for irrigation, and method for its manufacturing

ABSTRACT

The present invention relates to the field of extensible flexible hoses, especially but not exclusively intended for use for irrigation, and more specifically relates to a new configuration for such a hose, and the relative production process.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the field of extensible flexible hoses,especially but not exclusively intended for use for irrigation, and morespecifically relates to a new configuration for such a hose, and therelative production process.

BACKGROUND OF THE INVENTION

Flexible hoses are known for the passage of a fluid under pressure,mainly a liquid such as irrigation water, the configuration of which issuch as to ensure a significant (and automatic) elongation of the hoseitself when subjected to the pressure of the liquid inside it, thenretreating to the original or rest size when this pressure ceases, i.e.when the tube is emptied. In this way, the handling of the hose when notin use is much simpler and more convenient, due to the reduced overalldimensions.

Among the known hoses that can achieve such a performance such, one canfind different technical solutions that are conceptually different fromone another, the main ones being the following:

-   -   the solutions that provide hoses with a corrugated structure,        thus extensible in a bellows-like fashion;    -   spiral hoses, in which a wire, generally made of a plastic        material, runs in a spiral pattern along the body of the hose        (in a polymeric elastic material), and becomes extended in        response to the fluid pressure, causing the elongation of the        hose, while getting back to the shortened condition when the        pressure ceases;    -   hoses in which a layer of textile material is sandwiched between        two layers of polymeric elastic material so as to form a unitary        structure, the textile material being elastically extensible so        as to exert a control of the hose extension similar to that of        the above mentioned the spiral wire. This kind of hose structure        is disclosed in document EP3323468, in which the above-mentioned        textile layer, basically obtained by knitting, weaving or        knotting, is co-extruded and welded in a sandwich between two        polymeric layers.    -   composite hoses in which an inner tube made of polymeric elastic        material is simply inserted, in a loose fashion, inside a        tubular textile layer, remarkably longer than the inner tube and        therefore wrinkled in the rest condition; however, in response        to a radial expansion of the inner tube (subject to the fluid        pressure) becomes stretched until it forms a rigid barrier        preventing a further radial expansion, thereby forcing the inner        tube to extend in elongation.

Focusing on this latter type of solution, which is very interestingespecially because a remarkable elongation capability is obtained withreduced production costs, some significant advantages can neverthelessbe pointed out.

In the first place, the extension mechanism is such as to determine anabrasive action between the inner tube and the outer layer, in thephases in which the first expands and goes to find the stop action fromthe outer layer. As these abrasions repeat, with the continuous use ofthe hose, a rapid deterioration of the hose ensues, and the same hosecoms to an early breakage. Even more significant is the weakness at theconnections positioned at the ends, and indispensable for use. Asmentioned, the inner tube increases its diameter when the liquid underpressure passes, and, encountering the containment barrier from thetextile layer, it cannot continue to expand, so that a thrust isgenerated in the longitudinal direction which allows it to belengthened. However, in the first phase of the passage of the liquid—andat any subsequent moment of interruption and resumption of the flow ofthe liquid inside the tube—the tube undergoes an abrupt swelling in allits extension which impacts violently at the end junction point,generating a high risk of damage. At that point, in fact, the materialundergoes a particular stress capable of compromising the solidity ofthe bonds, until they deteriorate and become subject to tearing; thisfailure risk entails a clear limitation of the possibility of use and ofmaintaining the desired performance.

Moreover, the wrinkled start state of the outer layer in the hose restcondition causes, in this condition but also during the elongationphase, the possibility that the hose gets caught by protrusions presenton its path or in its use environment. The wrinkles also cause thedrawback that the hose gets soiled more easily, and is more difficult toclean, a drawback indeed also presented by other types of knownextensible hoses with a non-textile exterior, due to the stickiness ofthe material that forms the exterior wall of the hose.

Furthermore, it must be considered that the above-mentioned extensiblehoses are generally structured so that the diameter of the passage ductis, in the working condition, more or less double than that of the restcondition. In composite hoses with an outer tubular layer, due to theirextension system, the diameter of the outer layer (as already mentioned,substantially not expandable) clearly corresponds to the workingdiameter of the inner tube, and is therefore quite big even in the restcondition. Therefore, the hose is rather cumbersome, both in the workingcondition and even in the rest condition.

It must not be overlooked that, although relatively inexpensive (as itis not very sophisticated from the point of view of productiontechnologies), the assembly process with manual insertion of the innertube in the tubular outer layer still involves a complication and alengthening of the production times (and costs).

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome said drawbacks, byproviding a flexible extensible hose, in particular but not exclusivelyfor watering fluid, which has a special performance in terms of itsextension capability, at the same time ensuring increased durability andreliability with respect to similar known hoses.

A particular object of the present invention is to provide a flexibleextensible hose of the above-mentioned type, that takes up minimal spacein the rest condition as well as in the working condition.

Another particular object of the present invention is to provide aflexible extensible hose of the above-mentioned type, which has lowtendency to get caught on external elements in the environment in whichit is used.

A further particular object of the present invention is to provide aflexible extensible hose of the above-mentioned type, which has areduced tendency to collect and/or adsorb dirt from the environment, andin any case is easily and successfully washable.

An even further object of the present invention is to provide a flexibleextensible hose of the above-mentioned type, which can be manufacturedwith a single-stage productive process and thus with reduced productiontimes and costs.

According to the invention, these objects are attained by the flexibleextensible hose and its manufacturing process according to theinvention, the essential features of which are defined by claims 1 and 9here attached.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the flexible extensible hose and itsmanufacturing process according to the present invention will becomeapparent from the following description of embodiments thereof, madewith exemplifying and not limiting purposes, with reference to theattached drawings in which:

FIG. 1 is a perspective view of a hose according to the invention, withits relative end connectors, at one of which a hand sprinkler ismounted;

FIG. 2 is a perspective view of a hose piece according to the invention,broken so as to show its configuration, in a rest condition;

FIG. 3 is a side view of a hose segment in a rest condition, with acaliper tool showing its diameter, FIG. 3a being an enlarged detail ofthe same FIG. 3;

FIG. 4 is a side view of a hose segment in an extended or workcondition, with a caliper tool showing its diameter, FIG. 4a being anenlarged detail of the same FIG. 4; and

FIG. 5 represents in a perspective view a step of the manufacturingprocess of the hose according to the invention in a braiding machine.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the above figures, the hose according to the inventioncomprises an inner tube 1 made of an elastic polymeric material, in oneor more layers, obtained by extrusion, typically natural or syntheticrubber or other similar materials having suitable properties such asTPE, TPE-S, TPE-SEBS, TPE-O, PP/SEBS, PP/EPDM, silicone materials, inany case with a hardness preferably between 20 and 70 Sh A. The innertube 1 is covered in a loose fashion by a tubular outer layer 2 made oftextile material which, as will be better explained below, is made witha braiding process, adapted to produce an axially extensible pattern,directly around the inner tube 1 and so as to result in substantialcontact, but without adhesion, to the same in the rest condition.

The textile fibers used to braid the outer layer 2 are preferably madeof polypropylene (as a non-limiting example, with a linear density of1100 dtex and a torsion comprised between 60 and 100). Suitable yarnscan also be polyester, polyamide, polyethylene, para-aramid fibers andother fibers which are tendentially not elastic or otherwise withnegligible elasticity. The yarn can advantageously undergo a preventivebath to reduce its abrasiveness and therefore slow down itsdeterioration, for example with a coating substance such as polyurethaneor other materials of similar properties and suitable for the purpose.

Entering in further detail on the process for manufacturing the hose,with particular reference to FIG. 5, the inner tube can have variousdimensions, but for example it can be a tube having dimensions between 6mm and 10 mm (typically about 8 mm) as an internal diameter, and between8 mm and 14 mm (typically about 11 mm) as an outer diameter. Such a tubeis fed along its central or longitudinal axis X to a closed braidingmachine M of a known type for making tubular cords, for example with 24spindles, which provides for the realization of the textile outer layer.Some parts of the machine are actually represented in FIG. 5, without acomplete illustration or detailed description being necessary, giventhat, as mentioned, it is a machine known per se even if employed incompletely different contexts with respect to the one here considered(for example that of the production of tying ropes). A suitable machinecan for example be a vertical rotary braider such as, among the manyavailable on the market, the 120 Stitch model of the Italian company ETKs.r.l. (www.etkstl.it)

In the feeding motion the X axis of the inner tube is arranged(vertically) along the working/feeding axis X′ of the machine, i.e. anaxis perpendicular to the plane from which the spindles (and thereforethe rotating spools R that feed the yarn obliquely towards the braidingregion) rise.

According to an aspect of the invention the inner tube 1 is moreoverkept, through suitable stretching devices, in a stretched arrangement(always obviously along the axis X) for at least a segment whichcomprises the braiding region, so as to cause an elongation, which caneven be quantitatively small but in most cases will be advantageouslybetween 3 and 4 times the length at rest, preferably about 3.7 times.This stretch corresponds to a thinning of the external diameter of about5-6 mm (in the context of the basic dimensions indicated above), but ingeneral, depending on the starting diameter, it will possibly oscillatebetween 3 mm and 10 mm. Also the stretching devices, comprising inparticular roller systems distributed in number, configuration andactuation parameters which vary according to the amount of the desiredstretching, can be obviously devised or arranged according totechnologies already in use in braiding machines.

The textile layer, in the form of an outer tubular structure 2 whichremains completely loose, not adherent, with respect to the inner tube 1and which will itself define the outer surface of the hose withoutfurther layers thereon, is therefore constructed around an inner tubethus thinned. In this way, an outer tubular layer 2 is made which isadapted to take on substantially the same maximum diameter (the diameterobtained with the maximally compressed or “closed” yarn pattern, i.e.with fibers as close as possible to the plane orthogonal to the centralaxis X) with respect to the outer diameter D1 of the inner tube at rest.To this end, according to an advantageous aspect of the invention, abraiding angle α is set (i.e. the semi-opening angle of the conicalsurface on which the yarns lie when fed to the interlacing point) ofabout 15°-20°. This setup is obtained, for example, according to theembodiment shown in FIG. 5, thanks to a ring arranged coaxially with themachine axis X′, which with its internal diameter clamps the bundle ofwires coming from the spools at different angles and in any case greaterthan 20°, by forcing a homogeneous change of angle and at the same timecontrolling the height of the braiding region, ensuring that it remainsat a certain distance—useful for avoiding mechanical interference—withrespect to the device to collect the hose.

The tubular outer layer thus created will be able to prevent the radialexpansion of the inner tube beyond the diameter D1 of the restcondition, and then promote and assist its extension, with distensionand opening of its pattern (yarns that become more angled with respectto the plane orthogonal to the X axis). This aspect will be consideredin more detail hereafter, describing the working behavior of the hose.Returning to the manufacturing process, at the exit from the braidingmachine the inner tube 1 is no longer being stretched and elasticallyretracts, taking again the length and the diameter of the restcondition. Likewise, the pattern of outer layer 2, which at the time ofits formation on the thinned inner tube was more open and at the sametime left a certain free space or gap with respect to the outside of theinner tube, compacts itself, with a certain longitudinal retraction andradial expansion; the outer layer itself, in its maximum degree ofradial expansion, assumes the characteristics of a sheath that coversthe outside of the inner tube with a smooth and homogeneous appearance(FIG. 2).

The semi-finished product represented at this point by the assembly ofinner tube 1 and outer layer 2 is cut to the desired length to form ahose segment 10, and provided at its ends (see FIG. 1) with connectormembers 3, 4 which make tube 1 and layer 2 mutually integral (necessarycondition to ensure the automatic extension of the hose) and allow thehydraulic connection to a supply of pressurized water and to adispensing handpiece E. The actual hose is thus obtained, which ifsubjected to a liquid pressure between 2.5 and 4 BAR is able to extendautomatically about two times the original length at rest.

With particular reference to FIGS. 3 and 4 with relative enlarged views3 a and 4 a, it will be noted that in the rest condition (FIGS. 3 and 3a), the outer diameter of the hose is as mentioned—consistent with thediameter D1 of the inner tube 1 at rest (in this case, about 13 mm inspite of an outer diameter of the inner tube of 11 mm, due to theadditional thickness of the outer layer); moreover, one can notice therelatively smooth and compact structure of the outer layer 2 with aclosed pattern and yarns oriented in an almost orthogonal manner to theX axis. FIGS. 4 and 4 a show instead a working condition, in which thehose has extended, with the outer layer which has accompanied thisextension, reducing its diameter, due to a certain opening of pattern(fibers/yarns in this case more angled with respect to the planeorthogonal to the X axis). This is therefore the longitudinally extendedcondition of use, in which, this being a further aspect of interest ofthe present invention, if accompanied by the operator with a slighttraction force, the hose still extends until reaching up to three timesits own original length. Still during use, the hose does not show anynatural tendency to shorten, which occurs automatically up to itsoriginal length at rest at the time of emptying, when the hydraulicpressure inside ceases its exercise.

From the description above one can notice the significant advantages ofthe invention with respect to the known hoses with a loosely arrangedouter textile layer mentioned in the introductory part.

First of all, the dynamic interaction between the inner tube and theouter layer is such as not to generate significant abrasion phenomena,as the outer layer does not lengthen sharply and macroscopically betweenthe rest condition and that of use, indeed going to accompany and assistthe longitudinal extension of the inner tube. This results in lowerrisks of breakage and longer duration. Secondly, the compactconfiguration (both radially and axially) of the outer layer even andalready in the rest condition avoids entanglement or twisting phenomena,and prevents the collection of dirt, in any favoring the easy andeffective washability if the hose is used in particularly dirtyenvironments, for example muddy environments.

Again due to its construction, with the inner tube which when the liquidunder pressure passes tends to increase in diameter but promptly meetsthe resistance generated by the outer textile layer, and thereforeimmediately begins to lengthen while maintaining a diameter almost equalto that of rest (prerogative of the present invention and which marks asubstantial difference with respect to the known extensible tubes), thetube is of reduced bulk both during rest and operation, therefore moreconveniently usable and easier to store.

The manufacturing of the extensible hose of the present invention thentakes place with a single-stage productive process, combining the hosemanufacturing line with the machine that realizes the textile outerlayer. This speeds up production, with consequent economy, and makes itpossible to automate most of the hose construction operations, withobvious advantages on the cost of the product and on the reliablestability of its technical and qualitative characteristics.

The hose according to the invention is generally non-deformable, and itdoes not tend to twist or to form knots. The passage of liquid inside isalways guaranteed. No bottlenecks or obstructive folds are created whenthe liquid flows. The resistance to high pressures is high (compared tothe standard of the hoses usually employed in the irrigation sector) dueto the strong containment exerted by the textile pattern that covers theinner tube. Thanks to the materials used and the way in which they arecombined, the hose is still very light and therefore can be easilyhandled even by users without particular physical strength.

Compared to the hose and manufacturing techniques shown in EP3333488,the present invention adopts a completely different nature of productiontechnology; in the present case, in fact, there is no complex and costlyline of machinery for the co-extrusion of the polymeric tubes andconcurrent realization of the textile layer to realize a unitarystructure in which the textile layer is irreversibly sandwiched,incorporated and invisible between two polymeric layers, one of whichrepresents the outer layer of the hose. The very fact that the outerlayer is a polymeric one causes a rapid decay or at least an easydirtying of this known hose, which becomes—in particular after a certainuse—consequently unpleasant to the touch. Also from the point of view ofelongation, this type of known hose is not in any case capable ofensuring the performance of the hose according to the present invention.

Depending on the operating parameters chosen in the construction phase,including in particular the degree of stretching imposed on the innertube in the braiding step, the performance of the hose can clearly varyand be suitably optimized, depending on the specific workingrequirements. It should be noted in this regard that even with a minorstretch of the inner tube 1 in the feeding step, it will still bepossible to obtain a hose which, although not reaching the mentionedhigh extension performance, will still be moderately extensible andalways achieving at least partially, but in any case appreciably, theproduction and working advantages mentioned above. In addition toirrigation, which still represents the use for which the hose accordingto the invention is particularly suitable, the hose can in generally beprofitably used for any similar requirement of passage/distribution ofliquids but also and even more generally of fluids such as compressedair.

The present invention has been described so far with reference to itspreferred embodiments. In this regard, it is clear that the sizes andmaterials mentioned above represent exemplary indications, and that theinvention is not limited by them; it is generally to be understood thatthere may be other embodiments which refer to the same inventiveconcept, falling within the scope of the protection set forth by theappended claims.

1. Extensible flexible hose for transporting a pressurized fluidcomprising: an inner tube made of an elastic polymeric material adaptedto be extended along a longitudinal axis (X) starting from a restcondition in which the inner tube has a rest diameter (D1) and to becomeradially expanded starting from a rest condition; a tubular outertextile layer with a stretchable pattern, arranged outside said innertube in a loose manner with respect to said inner tube and coaxiallythereto with reference to said longitudinal axis (X), said outer layerbeing adapted to define in itself an outer surface of the hose with nofurther layers; and respective connector members to fluidically connectsaid tube to a feeding source of said fluid and to a fluid deliverynozzle, arranged respectively at a first and at a second common end ofsaid inner tube and said outer layer so as to make the inner tube andthe outer textile layer mutually integral in correspondence to saidends, the hose being characterized in that said outer textile layer isobtained by braiding textile yarns directly around said inner tube in alongitudinally stretched condition with respect to said rest condition,said tubular outer layer having a maximum diameter, obtainable with amaximum axial compression of its textile pattern in the direction ofsaid longitudinal axis (X), corresponding to said rest diameter of saidinner tube in said rest condition, said textile material of said outerlayer being a non-elastic yarn or a yarn with insignificant elasticitychosen among the following materials or a combination thereof:polypropylene, polyester, polyamide, polyethylene, para-aramid fibers.2. The hose according to claim 1, wherein said stretched condition ofthe inner tube is a condition in which the inner tube is 3 to 4 timeslonger than a rest condition.
 3. The hose according to claim 1, whereinsaid inner tube has an inner diameter of between 6 mm and 10 mm, and anouter diameter of between 8 mm and 14 mm.
 4. The hose according to claim1, wherein said elastic polymeric material has a hardness of between 20and 70 Sh A.
 5. The hose according to claim 1, wherein said polymericmaterial is chosen among the following materials or combinationsthereof: natural or synthetic rubber, TPE, TPE-S, TPE-SEBS, TPE-O,PP/SEBS, PP/EPDM, silicone materials.
 6. The hose according to claim 5,wherein said yarn is made of polypropylene with a linear density of 1100dtex and a torsion of between 60 and
 100. 7. The hose according to claim5, wherein said yarn is lined with an anti-friction substance such aspolyurethane.
 8. A method for manufacturing an extensible flexible hosefor transporting a pressurized fluid comprising the steps of: —feedingan inner tube made of an elastic polymeric material adapted to beextended along a longitudinal axis (X) and to become radially expandedstarting from a rest condition in which the inner tube has a restdiameter (D1), to a stretched condition along said longitudinal axis (X)with respect to said rest condition; —braiding around said inner tube insaid stretched condition a tubular outer textile layer with astretchable pattern, so that said outer textile layer becomes looselyarranged over said inner tube and has a maximum diameter, obtainablewith a maximum axial compression of its textile pattern in the directionof said longitudinal axis (X), corresponding to said rest diameter (D1)of said inner tube in said rest condition; —restoring the restcondition, said textile material of said outer layer being a non-elasticyarn or a yarn with insignificant elasticity chosen among the followingmaterials or a combination thereof: polypropylene, polyester, polyamide,polyethylene, para-aramid fibers; cut the assembly of outer layer andinner tube thus obtained to a segment of a desired length; —applying toa first and to a second end of said segment, so as to make the innertube and the outer layer mutually integral in correspondence to saidends, respective connector members to fluidically connect said tube to afeeding source of said fluid and to a fluid delivery nozzle.
 9. Themethod according to claim 8, wherein said stretched condition of theinner tube is a condition in which the inner tube becomes 3 to 4 timeslonger than the rest condition.
 10. The method according to claim 8,wherein said textile outer layer is braided with a rotary braidingmachine having a vertical axis (X′), said inner tube being fed with itslongitudinal axis (X) coincident with the vertical axis (X′) of themachine.
 11. The method according to claim 10, wherein the braidcomprised between 15° and 20°.